As is well known, in gaseous fuel carburetors, the fuel bowl, the needle valve and seat, and the float of the liquid fuel type carburetor are in effect replaced by a zero or low pressure demand type governor. A primary pressure regulator reduces the high gas pressure, such as that of L-P gas, to a relatively constant, low pressure, e.g. 6 p.s.i.g. Gas at the latter pressure is led into the demand governor to a valve which, as closely as possible, is biased just enough to maintain it in its closed position against the pressure of the gas at the valve seat. The valve is activiated usually by a diaphragm controlled linkage, one side of the diaphragm being open to the atmosphere, or to the throat of the carburetor up-stream of the venturi or other point relied upon to meter the fuel, and the other to the venturi itself or other metering point, as the case may be. When there is no pressure drop through the carburetor, the valve remains closed inasmuch as the pressures on both sides of the diaphragm are equal. When the engine is operating, the pressure drop through the carburetor creates a pressure differential between the two sides of the diaphragm, causing it to flex and the linkage to open the valve to admit gas to the carburetor. Since the extent of the valve opening is governed by the amount of movement of the diaphragm, and that upon the pressure differential between its two sides, and since the pressure differential in turn depends upon the speed of and load on the engine, proper proportionate amounts of gas are fed to the carburetor for varying engine speeds and loads.
Obviously, in order for the engine to function properly, the demand governor must be as sensitive and as proportionally constant in operation, with as little friction in the linkage, as is possible. Unfortunately, an arrangement which provides good, sensitive operation of the governor at idle and low engine speeds and/or loads tends not to provide the same at higher engine speeds and/or loads, and vice versa. The primary reason for this in most current governors is that the linkage interconnecting the diaphragm and the valve provides a relatively fixed amount of valve movement for a given amount of movement of the diaphragm regardless of whether the engine speed and/or load is low or high. If the valve movement is right for higher speeds and/or loads, it tends to be too much and too insensitive for low speeds and/or loads; if it is right for low speed and/or loads, it tends to be too little for higher speeds and/or loads. Furthermore, friction in the linkage also tends to upset proper movement of the valve, especially at low engine speeds and/or loads, and the bias on the valve towards its closed position, generally by means of a spring arrangement, tends to vary depending upon the degree to which the valve is open, whereas it should be constant as possible no matter how much or little the valve is open. Finally, the design of the demand governor should contribute towards ease and economy of its manufacture and assembly, using as simple and few parts as possible. The foregoing requisites and considerations are also generally applicable to demand type governors used to supply fuel to the burners of heating apparatus and the like.
The operation and requirements of demand type governors used for breathing purposes in "hostile atmospheres", e.g., aqua-lung diving apparatus and mine safety, firefighting and aircraft or high altitude breathing apparatus, are likewise essentially the same as those for internal combustion engine. In the breathing type apparatus, the compressed air stored in tanks is also first led through a primary type regulator before being presented to the demand governor through which the user breathes. The primary regulator reduces the high pressure air to a relatively constant low pressure at the governor in the case of breathing apparatus used adjacent ground level, to progressively lower pressures at the governor in the case of that for ascending in the atmosphere, and to progressively higher pressures at the governor in the case of that for descending in water, in order to balance the decreasing ambient pressures of the air and the increasing ambient pressure of the water, respectively. Here too, especially, the governor must be as sensitive and proportionally constant in operation as possible as the demands upon it range from low to high. If too much effort upon inhalation is required to open the inlet valve, the user, be he diver, fireman, pilot or whatever, may often unduely tire or frighten, as much for pyschological as for physiological reasons. Yet at the same time, the inlet valve must be able to open quickly and sufficiently to provide for large and rapid breathes. All of these aspects, as in governors for internal combustion engines, are affected by the nature of the valve operating mechanism and the uniformity of the bias on the inlet valve. Lack of friction and ruggedness of structure are especially important in breathing apparatus which particularly dictate that the governor have a minimum number of parts and interconnections between them. As in the case of internal combustion engines, it should also be easy and economical to manufacture and assemble.
Accordingly, the primary objects of the present invention are to provide governors of the nature described in which the demands of low and high operating conditions are better accommodated, in which friction between the parts is reduced, in which the closing bias on the inlet valve is uniform regardless of the degree of valve opening, which is simple and rugged in structure, and which is easy and economical to manufacture and assemble.